Support booking button doesn't work when sign_up_link is an empty string

[jdudley1123]

If the sign_up_link field is an empty string (rather than a null string) then the check fails and the view treats the empty string as a link.

fusebox-insights/app/views/offers/show.html.erb

Line 26 in 6a6b9ba

<% link = @offer.sign_up_link || project_offer_book_path(@project, @offer) %>